A guide wire for guiding a medical instrument such as a catheter to a predetermined position in a body cavity such as a blood vessel is required to have flexibility at its distal end portion.
Therefore, there is known a guide wire in which the outside diameter of an distal end portion of a core wire is made smaller than that of its proximal end portion, and a coil spring is installed on an outer periphery of the distal end portion (distal end-side small-diameter portion) of the core wire, thereby intending to improve the flexibility of the distal end portion (see, for example, Patent Literature 1).
In order to install the coil spring on the outer periphery of the distal end-side small-diameter portion of the core wire, both front end portion and rear end portion of the coil spring are generally fixed to the core wire by solder.
Here, Ag—Sn solder is used as the solder for fixing both front end portion and rear end portion of the coil spring to the core wire because of its low melting point and easy handling.
The solder penetrated into the interior of the coil at both front end portion and rear end portion of the coil spring comes into contact with the outer peripheral surface of the core wire, whereby the coil spring is fixed to the core wire.
In addition, a distal end tip is formed by any other solder than the solder penetrated into the interior of the coil at the front end portion of the coil spring.
In order to ensure the fixing ability of the coil spring to the core wire, however, it is necessary to sufficiently penetrate the solder into the interior of the coil at the front end portion of the coil spring, which is fixed to a distal end portion of the core wire, which has a minimum outside diameter. Specifically, it is necessary to penetrate the solder (Ag—Sn solder) into the interior of the coil in a range corresponding to about 6 pitches to about 8 pitches of the coil spring.
A portion (including the distal end tip formed by the solder) stiffened by the solder filled into the interior of the coil is formed at the distal end portion of the guide wire produced in this manner.
The length (length corresponding to the distal end tip and about 6 pitches to about 8 pitches of the coil) of this distal-end stiff portion is about 0.8 to 1.1 mm.
In order to achieve low invasiveness in a patient, it has been recently desired to miniaturize medical instruments.
With this desire, there has been a demand for making the diameter of a guide wire small, and so the present inventors have developed a guide wire having a smaller wire diameter (0.010 inch) than that (0.014 inch) of a conventional one.
The guide wire of 0.010 inch can greatly contribute to the miniaturization of medical instruments such as catheters.
In addition, this guide wire is also good in operability upon accessing, for example, a micro-channel in CTO (chronic total occlusion) lesion.